1. Field of the Invention
The present invention relates to a fuel cell.
2. Discussion of the Background
For example, in a solid polymer electrolyte fuel cell, a solid polymer electrolyte membrane formed of a polymer ion exchange membrane is employed. In the fuel cell, each unit cell is formed by sandwiching an membrane-electrode assembly (electrolyte-electrode assembly) (hereinafter referred to as an MEA) between separators (bipolar plates), the electrolyte membrane-electrode assembly including a solid polymer electrolyte membrane and anode-side and cathode-side electrodes that are disposed on the respective sides of the solid polymer electrolyte membrane, the anode-side and cathode-side electrodes each including an electrode catalyst layer and porous carbon layer. Normally, a fuel cell stack, in which a predetermined number of unit cells are stacked, is used as, for example, an in-vehicle fuel cell stack.
In general, a fuel cell includes what is called an internal manifold which is provided with an inlet communication hole and an outlet communication hole, the communication holes extending in the stacking direction of the separators. A fuel gas, an oxidant gas, and a cooling medium are then supplied from respective inlet communication holes to a fuel gas passage, an oxidant gas passage, and a cooling medium passage, respectively, that is formed along the planar direction of the electrode surface, and then are discharged into respective outlet communication holes.
For example, the separator for fuel cells disclosed in Japanese Unexamined Patent Application Publication No. 8-222237 includes a separator plate 1 as shown in FIG. 16. The separator plate 1 is formed of a metal plate, and a large number of projections 2a, 2b are formed on the front and back surfaces of the metal plate by emboss press forming or dimple press forming. In the separator plate 1, there are formed manifold loading through ports 3a, 3b, 3c, and 3d outside the projections 2a, 2b forming region, in order to load respective gas manifolds.
The manifold loading ports 3a, 3b, 3c, and 3d are used as, for example, a fuel gas introduction manifold, an oxidant gas introduction manifold, a fuel gas discharge manifold, and an oxidant gas discharge manifold, respectively.